This invention relates to solving gear problems on photoreceptor drums as used in Xerography and more specifically in the toner cartridge remanufacturing industry. This includes copiers, laser printers and facsimile machines.
CANON has designed an all-in-one cartridge as seen in U.S. Pat. No. 4,975,744 issued Dec. 4, 1990 assigned to CANON. Several companies have used these cartridges in laser printers, copy machines and facsimile machines, each with the varying printer engines and a different nameplate. Originally, these cartridges were designed to be "disposable". However, after the first all-in-one toner cartridge was introduced, it did not take long before laser cartridge remanufacturers such as myself began remanufacturing these cartridges. These "disposable" cartridges were designed to function for only one cartridge cycle without remanufacturing. The remanufacturers had found certain components that needed replacement on a regular basis. In 1990, the first aftermarket photoreceptor drum became available for use in remanufacturing the all-in-one cartridge of the "SX" engine variety, the most popular printer cartridge from around 1987 through 1993 at the time of this writing. When the long-life photoreceptor drum became available, the entire remanufacturing industry turned around and gained great strength and began a huge growth surge that still continues. In October 1993, HEWLETT-PACKARD, the largest seller of this printer engine using the all-in-one cartridge, entered the cartridge remanufacturing industry with the "Optiva" cartridge, further increasing the size as well as credibility of this relatively new industry. However, this relatively new industry grew from the all-in-one cartridge shortly after its debut. Before the introduction of the long-life drum, sometimes called the "superdrum" or "duradrum", the SX cartridge would last for around three cartridge remanufacturing cycles at best, since the actual useful life of the OEM drum was three cycles. However, the long-life drums got their names from the fact that they were designed to last for many remanufacturing cycles or recharges as they are sometimes called. Typically, the long life drum can last for ten or more such cycles, unlike the typical OEM(Original Equipment Manufacturer) drum. With the additional developments of drum coatings, originally designed for OEM drums, the long-life drum may last for many additional cycles. Some coatings, in theory, were designed to be dissolved and removed from over the drum surface every 1-3 cycles, so the drum life of the long-life drum almost seems limitless.
However, when the photoreceptor drum gets used over and over and over, the mechanical life of the moving parts may be the limiting factor of the length of useful life of the photoreceptor drum. Consequently, it is quite common to see the photoreceptive component of the drum outlive the mechanical components. For example, one problem is that after a large amount of use, say one to three or more recharge cycles, the gears may slightly wear in a way that may not be discernible to the average remanufacturer. The cartridge may appear normal, but have an unobvious problem that is difficult to detect from this wear. This problem has been analyzed in tests involving component switching. It was determined that the photoreceptor drum was the culprit. After closer inspection, it has been found that the problem resulted from the metal drum shaft wearing the plastic hole in the gear, generating an oversized and often oblong hole. It makes sense for a disposable cartridge that is to be used one time to use a plastic wearable component. This will generate the need for brand new cartridges rather than remanufactured ones. Whether the OEM manufacturer is designing these components overseas with such profit motivations is not the point. The disclosed invention has multiple improvements over this state-of-the-art gear set. One of the goals of this invention is to describe a more wear-resistant gear. It should be pointed out that it is rumored in the industry that the gear designs are patented and it is rumored that lawsuits over the design of these plain patented gears are taking place at this moment. So, clearly an alternative gear is needed anyway. One of the wear problems of this OEM gear is that it wears in the center hole and becomes out-of-round. Once it is out-of-round, oblong or otherwise disfigured, it causes an image distortion on the output page. This disfiguration can cause other wear problems in the cartridge and in the printer.
A second photoreceptor drum gear problem involves the grounding contact. The metal drum shaft on one side is electrically connected to the rotating photoreceptor drum to provide a ground to the inside wall of the drum, a necessary design feature. However, with the drum gear rotating with the stationary drum shaft inside, this contact involves a stationary, grounded drum shaft touching a rotating spring-clip contact. This rotating spring-clip contact is contacting the drum shaft tip and rotating with the drum, and often is designed to essentially scratch into the inside wall, usually aluminum, of the drum to insure electrical contact. One problem that occurs is that a thin yet invisible or opaque layer of insulative oxidation, toner dust, or other insulative debris may form a thin coating on the grounding clip or on the tip (contact area) of the drum shaft that prevents or partially may prevent the grounding function from taking place. In other words, the contact surface area is not great, making the typical design more prone to inconsistent grounding. It should be pointed out that in a 360 degree drum rotation, if only a fraction of a degree is insulated and loses contract for ever so brief an interval, each rotation or even every five rotations, this miniscule partial loss of contact can cause very serious image problems. One such problem is erratic print on the output page in places where it is not desired. One solution to the problem has been the use of conductive grease between the spring-contact and drum shaft. However, the conductive grease will typically not last for an entire cartridge cycle although it has been a big help. The conductive greases have two problems. First they won't last a full cycle as stated. Second, some conductive greases harden part way through the cycle and lose their properties. Another problem with the gear design of prior art is that the spring contact clip may lose resiliency or accumulate a thin layer of insulative oxidation or toner and thereby lose its electrical contact in the process. One partial solution is to use emery cloth, sandpaper or other abrasive to file, sand or grind the drum shaft tip or gear's spring-contact to clean it However, there is not a guarantee of perfect contact for an entire cycle since corrosion may occur and toner as well as plastic ground gear-tooth bits may form a thin insulative coating mid-cycle.
There is a second fix to the gear problem. Some photoreceptor drum gears have been designed using a conductive plastic. The conductive plastic gear does not require a spring-contact that touches the drum-shaft's tip. Instead, the conductive plastic gear rotates around the drum shaft and contacts it in the shank over a greater surface area. However, many electrical contact problems have been reported about the use of plastic conductive gears. Loss of continuity takes place. It seems to be from the loss of conductivity after many drum rotations. Perhaps the worn conductive plastic changes state from frictional heat at the contact surface. Perhaps toner insulates it and wears into the plastic, camouflaged. Perhaps the conductive plastic, with metal or graphite particles contained therein, has a wear effect wherein the metal conductive particles migrate away from the contact surface where it contacts the drum shaft. In any case, whatever the reason, plastic conductive gears do not have the desired reliability for drum gears, although it is a clever idea.
Because of the above described problems of photoreceptor drum gears, including the wear problem and the decreasing electrical contact problem in time, this invention has been developed. The invention solves both the wear of the inside gear hole problem as well as the problem of the decrease of electrical contact with time.
There is another gear problem in the industry associated with inserting the drum shaft into the gear and drum. This is a particular problem of the LX gear in the HEWLETT PACKARD LASERJET SERIES IIP. Often times the cartridge recycler, after pushing the smaller diameter drum shaft or shaft into the gear bushing and drum, thereby locking in the gear, gets an unwanted strange dark page of output. This is the result of pushing the drum shaft too far through the gear bushing. The end of the drum shaft is pushed past the drum gear's spring-clip contact, eliminating or weakening the electrical connection and causing the grounding function not to occur. This is a very common problem in the recycling industry, but many recyclers or remanufacturers don't know that the above solution is to avoid pushing in the drum shaft too far. Another solution involves loosening the two screws that hold in the gear bushing that locks in the drum shaft. However, this problem is prevented by using the various gear modifications of this invention, since greater, alternative grounding contact is achieved.
There is yet another gear problem in the toner cartridge industry. This problem is most clearly seen in the HP LASERJET SERIES 4 cartridge of the EX printer engine type. The wear resistant plastic, nylon or TEFLON gear has a shaft protrusion that was cast into the gear. This gear shaft has a small centered hole. This gear shaft fits into a hole in the waste toner hopper assembly. This hole tightly holds the gear shaft to allow it to freely rotate straight and true. Furthermore, the hole has a hollow cylindrical nipple or raised rim reinforcement. The problem lies in the fact that the hole and its reinforcement each are made of a black ABS type plastic. Since the ABS type plastic in the waste toner hopper assembly is much softer than the wear resistant nylon or TEFLON like material, it begins to wear. It is commonly known in the cartridge recycling industry that the gear shaft wears a larger hole in the waste hopper assembly hole, often oblong in shape, in the location where the gear shaft turns. Once this hole enlarges, however, the toner cartridge is useless and unusable, because the untrue rotation has such a detrimental effect on the quality of the image and function of the toner cartridge. Typically, the EX toner cartridge, according to data, can be recycled three times maximum, because this oblong wear pattern in the waste hopper assembly is the limiting factor. It is because of this described problem that another embodiment of the invention has been developed.
Other toner cartridges, such as the ones described previously, oftentimes have a nonconductive gear with a protrusion similar to this gear shaft that rotates inside a reinforced hole of ABS plastic. However, the wear in the ABS plastic was not as noticable as in the EX toner cartridge described above. First of all, rather than using a gear shaft, a cylindrical reinforced hollow rim is molded in the gear. This rim, of greater diameter that the gear shaft described above, acts like a rotating alignment bushing inside the cartridge toner hopper. The rim rotates inside a hole in the ABS type plastic. However, unlike the EX cartridge, this gear rim (as for example in the SX toner hopper assembly) has much less wear. But it eventually does wear. The problem with all of these gears may be solved in a similar manner.